TLH in 401(k): No

One of the most common misconceptions about tax-loss harvesting is that you can harvest losses from a 401(k), IRA, or other tax-deferred account. You cannot. Tax-loss harvesting requires a taxable event; tax-deferred accounts have no taxable events until withdrawal, and the rules governing withdrawals make harvesting meaningless. Understanding why is important for any investor with retirement accounts, which is nearly everyone.

Key takeaways

• Tax-deferred accounts (401(k), IRA, Solo 401(k), SEP-IRA) generate no taxable events during accumulation; losses cannot be harvested.
• Roth IRAs and HSAs are tax-exempt, not tax-deferred; losses are similarly non-deductible.
• If a 401(k) position falls below cost basis, the loss simply sits there; there is no mechanism to use it to offset other income.
• The 401(k) is sheltered from tax, which is good, but it also means harvesting—a tax strategy—cannot apply.
• For investors with substantial 401(k) balances and small taxable accounts, harvesting options are limited; the focus should shift to strategic asset allocation and rebalancing within the 401(k).

Why tax-deferred accounts eliminate harvesting

The wash-sale rule and all loss-harvesting mechanics exist because the IRS wants to tax capital gains. If a security is held in a taxable account and you realize a loss, the IRS recognizes that loss on your tax return and allows you to use it to offset gains or income.

A 401(k), by contrast, is exempt from this taxation during accumulation. When you contribute to a 401(k), the contribution and all gains within the account are not taxed until you withdraw them in retirement. The IRS has already "given you" the tax break upfront (via the contribution deduction); it does not want to give you an additional break by allowing you to harvest losses within the account.

More precisely: there is no taxable event within the 401(k). When you sell a losing position inside a 401(k), no capital loss is recorded anywhere. The account statement shows you now have cash (or a different holding) instead of the old position, but there is no "loss" reported to the IRS because the 401(k) is not a taxable account.

Example: a 401(k) loss vs a taxable loss

Scenario A: Taxable brokerage account

• You buy 100 shares of VTI at $250/share = $25,000 cost basis.
• You sell the VTI at $200/share = $20,000 proceeds.
• Realized capital loss: $5,000.
• You report this loss on Schedule D of your Form 1040.
• You can use this loss to offset capital gains or (up to $3,000 of) ordinary income.

Scenario B: 401(k) account

• You invest $25,000 in VTI in your 401(k).
• The VTI falls to $20,000 in value.
• You sell it and buy something else (or hold cash).
• Realized loss: $0 (from the IRS perspective).
• You report nothing to the IRS about this transaction.
• You cannot offset gains or income with this loss.

The difference is tax treatment. The IRS taxes gains/losses only in taxable accounts. In a 401(k), there is no taxation (and thus no deduction) until withdrawal.

Roth IRAs and HSAs: also non-harvesting

The same logic applies to Roth IRAs and HSAs, though they are tax-exempt (not tax-deferred). These accounts generate no taxable income while you hold them. You contribute after-tax dollars, the account grows tax-free, and you withdraw tax-free (at age 59½ for IRAs, anytime for HSA medical expenses). Because there is no taxable event within the account, losses cannot be harvested.

If you hold a diversified portfolio in a Roth IRA and one position falls to a loss, you cannot use that loss to offset a gain elsewhere in the Roth. The loss simply stays within the Roth as an unrealized loss. If the position eventually recovers, great; if not, the loss is permanently hidden from the tax system.

This is actually fine. The Roth IRA shelters you from taxes entirely, so losses are less relevant. But it is important to recognize that harvesting is not an option within Roth accounts.

What investors with 401(k)-heavy portfolios should do instead

If your net worth is primarily in a 401(k) (common among employees with good employer plans), and your taxable account is small or nonexistent, tax-loss harvesting is not available to you. Your tax-optimization strategy should focus on:

1. Maximizing tax-deferred contributions: If you have a Solo 401(k) or access to a SEP-IRA, contribute the maximum allowed. The deduction is more valuable than harvesting.

2. Choosing tax-efficient funds within the 401(k): Use low-turnover, low-cost index funds inside the 401(k). The account is tax-sheltered, but the funds you choose still matter for expense ratios and tracking error.

3. Rebalancing carefully within the 401(k): When you rebalance, sell winners and buy losers if necessary to maintain your target allocation. You are not harvesting (there is no loss to harvest), but rebalancing is still tax-free within the 401(k).

4. Strategic withdrawal sequencing in retirement: In retirement, you can control the order in which you withdraw from taxable, Roth, and 401(k) accounts to minimize lifetime tax. This is your long-term tax optimization tool.

Comparing account structures for tax efficiency

Account Type	Tax Status	Harvesting Possible?	Example
Taxable brokerage	Taxable	Yes	Regular investment account with a broker
Traditional 401(k)	Tax-deferred	No	Employer retirement plan, deductible contributions
Roth IRA	Tax-exempt	No	Roth retirement account, contributions post-tax
Traditional IRA	Tax-deferred	No	Individual retirement account, deductible contributions
HSA	Tax-exempt	No	Health Savings Account, triple tax advantage but exemption applies
Solo 401(k)	Tax-deferred	No	Self-employed person's retirement plan
SIMPLE IRA	Tax-deferred	No	Small business retirement plan

Decision tree for harvesting eligibility by account

Related concepts

• What Is Tax-Loss Harvesting?
• Long-Term Investing Essentials

Next

We have now covered the full landscape of tax-loss harvesting: how it works, the rules that govern it, and when it is not applicable. In the final chapter wrap-up, we synthesize these concepts into an action plan for any investor considering this strategy.